** Editor’s Note: The staff of Scienceline is taking a short break to work on future stories. This article originally appeared February 27, 2008.**

For decades, the Big Bang has been taught in high school physics classes as the leading theory for the way the universe began. But despite the overwhelming evidence supporting it, several questions linger for physicists. How could something come from nothing? And why do the laws of physics not hold up at the bang?

Now, some scientists say that the Big Bang was not the beginning, and that there was a universe before ours. The key is a new concept of gravity, which explains how such a universe could exist without violating the laws of physics.

If correct, Martin Bojowald, main architect of the theory and Penn State physicist, will have overcome the inability to explain the early universe. This problem has left scientists, including the likes of Einstein, perplexed for years.

“In my opinion, this is the single most embarrassing problem of physics,” said Max Tegmark, an astrophysicist at Massachusetts Institute of Technology.

In simple terms, Bojowald’s theory, published in August’s Nature Physics, can be described as a Big Crunch followed by a Big Bounce. He suggests there was a universe before ours that was collapsing and getting hotter (the crunch). Then, when it reached a maximum density and temperature, it was driven apart (the bounce), forming our current universe.

The main ingredient of Bojowald’s crunch-bounce theory is loop quantum gravity, a new concept that combines the traditional understanding of gravity with the quantum effect, which says that matter behaves differently at the subatomic level. Many scientists believe it is the absence of the quantum effect in equations that describe the Big Bang that lead to impossible phenomena like infinite temperature and density.

In Bojowald’s model, without the quantum effect, there would be no force to drive it apart; the collapsing universe that preceded ours would simply collapse into oblivion. But with the quantum effect, reaching a certain temperature and density threshold would trigger repulsive forces to drive the universe apart.

“The repulsive forces would stop the complete collapse and also turn it around into an expansion,” Bojowald said, effectively preventing temperature and density from approaching infinity.

While the crunch-bounce solves this problem of infinite temperature and density, the challenge becomes finding evidence to support the existence of the previous universe. To see if there was anything before the bounce, you would have to observe the distribution of particles small enough to have passed through the very dense early universe. Currently, neutrinos, very tiny particles that travel close to the speed of light, fit the bill. But they are very hard to detect.

If the method of detecting neutrinos improves, they could point to a previous universe. However, Bojowald said that in order to do this he first needs to answer the following question: If there was a universe before the bounce, what would the distribution of neutrinos look like today? Then, using equations and computer simulations he could make predictions and compare those with actual observations of neutrinos.

Other scientists find the crunch-bounce theory intriguing, but point out that there are still problems. Sean Carroll, a physicist from the California Institute of Technology, said his main concern is that the model overlooks the idea of entropy.

One way that entropy can be defined is the tendency for particles, energy or heat to disperse rather than remain clumped together. For example, smoke leaving a chimney will spread out, rather than stay in one place, thus increasing in entropy.

The expanding universe also acts in this manner and is continually increasing in entropy. An unusual observation, according to Carroll, is the universe’s low entropy near the Big Bang. Since this is such an unusual phenomenon, he said it was necessary for any new theory to explain why entropy is so low at that point.

“It would be like walking into a room and finding all the air molecules on one side,” Carroll said.

Aside from the crunch-bounce theory, other credible challenges to the Big Bang are emerging, too. Cambridge’s Neil Turok and Princeton’s Paul Steinhardt have a model they call the Cyclic Universe. These physicists believe that the Big Bang was not a unique event, but one in a series of bangs with more bangs yet to come.

Bojowald’s theory does not discount this idea of “multiverses.” And neither theory estimates the number of previous universes or when the next crunch will happen. Turok and Steinhardt’s theory differs from Bojowald’s mainly in the mathematics they use to describe it.

They explain their model using string theory, a branch of physics that views matter as one-dimensional “strings.” Using the equations of string theory, they come up with a different picture of the early universe.

Like Bojowald, they were driven by the belief that the current Big Bang model leaves too many unanswered questions. Steinhardt said that the more scientists understand about the universe, the more the current model does not work. “Maybe we’re on the wrong track,” he said.

So far, though, none of the new models have overturned the Big Bang to emerge as the leading alternative, primarily because proving the existence of a previous universe is so difficult. Steinhardt says much more data and evidence are necessary before a paradigm shift can occur. “Most of us will stick to something until forced to give it up,” he said.

But even if these new ideas about the origin of the known universe are correct, they cannot address the ultimate questions: What came before all of those previous universes and Big Bangs? When did it all begin?

“We’re not going to actually answer the question of where the beginning was,” Bojowald said. “We’re just pushing the beginning back in time.”

Are we, then, edging back towards the universe having always existed, if we consider whatever there was before BB as being part of the universe? This seems as improbable as does the idea that the universe created itself from the absolute nothing. In an eternally existing universe, I can´t see how you can have events, like me typing on my computer at this moment (in my time). Any event would surely have occurred an eternity ago in an eternal universe and hence would not have occurred at all. The only eternal universe I can imagine would be one with nothing but totally empty space, where no events ever can or do occur and also without “quantum fluctuations”.

maybe in 10,000 years we might begin to have the intelligence to start to understand where it all came from. the only thing wrong with all the theories floating around is that we have the audacity to think with our limited intelligence we could begin to understand any of it. when is science going to wake up and realize we are still in single cell state. We marvel at all the things we have done and we are still that 3 feet high half monkey running from the lions trying to keep from being eaten of killed by the nearest clan. People string words together like they know what they are talking about and they know nothing.

1. This theory doesn’t really answer any questions, it merely moves them back in time. Instead of asking where our universe came from, we now ask where the previous universe came from.

2. I thought this theory had already been thrown out. Years ago, we had the oscillating universe theory. For that to be a valid theory, the universe would have to be expanding at a decreasing rate, which is the opposite of what we see.

If there had been a previous universe, its total energy content would have to be the same as ours (conservation of energy/mass). If it didn’t have the energy to infintely expand, then our universe wouldn’t either. If it did have the energy to infinitely expand, then our universe would never have been born. Again, this is the opposite of our astronomical observations. On this basis alone, I think the theory described is invalid.

Cosmological observations provide an incredibly rich set of clues to the pre-big bang universe. Do you see any flaws in: The pre-big bank universe at BigCrash.org?

…
In the beginning (in the pre-big bang universe) there was only the vast vacuum of space and time. But this vacuum was not sterile, it was seething with vacuum energy. This vacuum energy field permeates and defines the universe, an astronomically large sphere of energy. And just as matter generates gravity by warping space and time, so does energy and this is the force that defines the size and shape of the universe, and also the force that bestows mass on matter…

…When a virtual matter/anti-matter pair becomes a matter matter pair, the virtual particles are no longer able to mutually annihilate and they become real, stealing energy from the vacuum energy of space. This is the mechanism of slow matter creation in the first phase of the pre-big bang universe. Over perhaps a billion billion years, clouds of matter form over the entire universe, and eventually coalesce into cosmological bodies and eventually the first pre-big bang black hole, which starts the second phase of the pre-big bang universe, fast accretion of matter from vacuum energy by black holes…

“Cosmological observations provide an incredibly rich set of clues to the pre-big bang universe. Do you see any flaws in: The pre-big bank universe at BigCrash.org?”

I really don´t know where you get this from, as there is no evidence at all about a pre-BB universe, let alone “incredibly rich set of clues”.

This is from Stephen Hawking´s “A Briefer History of Time”:

“Correspondingly, if, as is the case, we know only what has happened since the big bang, we cannot determine what happened beforehand. As far as we are concerned, events before the big bang can have no consequences and so should not form part of a scientific model of the universe. We should therefore cut them out of the model and say that the big bang was the beginning of time. This means that questions such as who set up the conditions for the big bang are not questions that science addresses.” I don´t see much hint of him knowing anything about the rich clues about any pre-BB there might have been. However…I don´t really understand why events before a big bang can have no consequences, particularly as they were probably responsible for the BB in the first place. I also note that BB itself is coming under increasing attack.
I find it hard to accept that the whole universe could have been concentrated at a point at infinite density. What is “infinite density”?
Also, what caused BB? A cosmologist that I asked said that it happened for no cause, but I don´t believe that a status quo can be interrupted for no cause. Maybe we don´t or cannot know the cause, but I´ll bet there was one. (In a subsequent email he asked me how you go south when you get to the south pole. I´m still trying to work out what he is saying.)

Obviously ,science can only prove a theory from what it can observe or measure.However, we seem to forget or WISH to forget another pre Big Bang theory…….GOD.

Where did God come from ?If he is perfect he is eternal no beginning or end.The Mona Lisa may be considered a perfect piece of art but it’s origins were a crude piece of canvass and selection of oils.Its state was only improved upon.

PERFECTION thus by definition is eternal.GOD would explain EVERYTHING.QUITE NEATLY…….perhaps scientists need to be brave and accept an alternate truth just as Gallileo and Darwin made many of faith to be brave in thought!

I can hear all your groans from here but please do not dismiss out of hand…

@Chris Stewart:
I agree, if you look at the definition of science, it about every force that is visible or whos effects are visible. Fair enough. Although, it fails to address the possibility that humans cannot possible measure some things or imagine things that exist but we don’t know. I find it a bit strange when scientists say, earth was the only planet to have a fine tuned environment for life. Well, what if life was fine tuned through evolution to fit earth? the same argument applies to extra terrestrial beings, why can’t a different life form exist on mars? can’t a different kind of life evolve that we cannot even begin to comprehend?

We as humans can’t comprehend that time is truly infinite. I’ll quote The Matrix, “Everything that has a beginning, has an end”. That’s all we can understand at this point in time because it makes us feel comfortable and safe.

In my opinion, there was definitely a Big Bang, and before that there was a “Big Crunch.” Before that Big Crunch was a long period of time where the universe was in a state similar to what we see now. Yes, the universe is expanding now, it seems like, but years from now, it will stop expanding and will begin to contract to create that new “Big Crunch” only to begin to create a new universe with a new Big Bang.

Maybe humans will never understand infinity because in our world, everything that does start eventually has to end and that’s what we know.

…but now that I think about it, maybe my opinion falls into this “safety zone” i speak of because that’s what makes me comfortable. Making the excuse that time is infinite, and, because I am not a religious man, I feel comfortable telling myself that there was never a single force that created the building blocks of the universe and “space” itself. There was never a single force that had the immense power to do that, or take everything we know away with the snap of the fingers.

How about multiverses. Each expands from its own big bang. Sometimes they are close enough to each other that they expand into each other’s space. Where they overlap the black hole seed of a new big bang begins to form.

Maybe that seed begins to pull from each of the two “universes” and collapses from its own gravity until it hits a critical point and you get a new big bang.

Or maybe it can never reach the critical point, because too much of the matter from the previous 2 universes has dissipated out in the other direction. Remember they had to reach that same critical mass in order to have exploded in the past. In that case, maybe a third universe comes in as a trigger, spinning like a buzz saw.

In the 2-universe case, you might expect a disk shaped signature in the new universe, representing the gradual overlap of the 2 previous universes. Or you might find 2 poles, representing the central bulk of each of the 2 previous universes that got sucked in more rapidly at the last minute.

In the 3-universe (trigger case), you might expect a disk plus some other mass coming in at an angle.

In any case, it seems we would expect low entropy right after the big bang (as observed) because the crunch has pressed clumpy matter into more homogeneous plasma. After the bang, it spreads out, cools off, and gets clumpy again.

There is another explanation for what was there at the beginning.
Perhaps the universe was always there, and will always be there. All the evidence for an expanding universe and the big bang, is biased on measuring the rate of expansion of the universe using the Doppler effect. If the Doppler effect could be explained by another mechanism, such as a natural shift in light wave frequency as they travel through large distances in space. Then we could have a universe that is not expanding overall at all.
Some recent evidence form the study of black holes would suggest that there is an upper limit for the size of black holes. There is also evidence that all galaxies have black holes at the centre. Could these black holes be creating the stars in the galaxies not devouring them. Perhaps there is a balance created in a galaxy where the stars are constantly being recycled by the black hole at the centre. The background radiation attributed to the big bang, may only be the light coming from galaxies so far away that the light is shifted into the microwave spectrum.
Perhaps the universe was always there and goes on forever with no end. Our only concept of time is local. Just because all the local evidence would seem to support the idea that everything has a life cycle, does not mean that the universe has a life cycle.

the Universe runs by immutable laws, the Big Bang requires that these laws which hold the very fabric of the universe together be broken…how is this possible?
The further looked into, the deeper the problem will become, and the only way it is explainable by our finite minds is to put our faith in not the imaginations of men whose paradigms shift and change at every whim and fancy, but in the hands of the one who created it in the first place.
I can’t logically come to any other conclusion, I don’t like it, but face facts, there appears to be something more like a mind behind this universe than anything else…what power!

I have been saying for years before anyone knew that every galaxy has a black hole within it. My theory is this, eventually every galaxy will be swallowed up by their own black holes, then all black holes will swallow one another to form a large supermassive black hole that will swallow all matter and dark matter in all the Universe. This will eventually cause an increase in temparture and pressure at the other end that we know nothing of, but what if the other end will be the new Universe where it will all be released again for a new bang. Just a thought!

Alright, I’m thirteen. My idea of the big bang and how it started was that it was started by a type of atom which consisted GRAVITY, LOW PRESSURE, and HIGH PRESSURE. Gravity broke off which started the “Big Bang”. I think this because it, to me, makes the most sense. One: The idea of the previous universe contracting back and reflecting with the power to make a new universe is wrong. Two: “dark matter” is pushing out the universe, so how can it retract? Anyway, this theory has many flaws. This is my theory!

All plausible explanations, but in my opinion there is too much intelligent design in everything studied to allow acceptance of the big bang without a supreme person to cause it. I can accept the spatialization of time, and that time would not have existed before the BB, but matter itself had to result from some action or thought. It’s the cause and effect idea again, I just can’t get around it.

Well for starters if you want to find some facts, please visit CERN or FermiLab. Digits galore! But no this is not a new theory, its been around for a few decades if I remember right, yeah it was this really old guy named Einstein. And Mr. Ware, if “God” was real, physics wouldn’t work.

I have a theory of my own, that actually holds a distinct validity. Granted I am only 17, but trust me, it makes sense.

Obviously, something had to exist before the BB! We will never know what; we can’t, because we weren’t there. There will be theories abundant, but we will never truly know! When did everything all start, when will everything end and what was before that and what will be after. There had to be something before that and there will have to be something after! To really know, we would have had to been there, observing and learning.

Accordingly to Einstein, time slows in the presence of large mass. The early universe was a very large mass, and so time slowed right down , right down to the point where it stood still. The view of the universe as 13.8 billions years old is measured in the time of today, but with time dilation, the real age is infinite. There is no beginning to the universe. Conjecture of an earlier time is in the realm of religion.

Similarly, gravity could not have existed as a force until the universe had expanded beyond its Swartzchild radius. Otherwise it would have formed a supermassive black hole, but it didn’t. The birth of gravity was delayed until at least the time of the CMR(cosmic microwave radiation), at the very least.
This may have implications for the validity of inflation theory and so on…

If there was a creator, then it certainly wasn’t a ‘god’ as described in any of the religious texts, as there is zero evidence of a god existing. Therefore the creator (if there is one) created the universe and then buggered off.

Seems to me that we all think too much about “the minutiae”, loose our place on the page, just end up with our heads up our own backsides contemplating nothing other than our own pet theories. We then rush to pick up swords to defend whatever that may be.

Even the most “brilliant” theorists among us know in their hearts that what they have just theorized is not “the final and definitive answer” but simply the answer that makes the most sense within what we know to date, and that is not very much. By whatever means we humans were first created, it’s not having “a soul”, (whatever one of those is) that differentiates humans from most else, it is our insatiable curiosity and our unflagging and unstoppable desire “to know more”.

A monkey “knows” that it likes a banana, but has no idea, and cares even less, where it came from, or, how it came to be a banana, it lacks that special spark of curiosity that humans have. If you took that away from us, and we were all as contented as a well fed monkey, would our lives be any the better for it; would we not have made the mistakes we have made and the lessons we have learned by making them; would it be of any importance to us where we came from; how it came to be and where do we go from here? I think not.

The development of our knowledge and understanding is what we do; we can’t stop ourselves; and; we don’t always get it right; but that is because we are simply “a work in progress”, we always will be, because “learning” is an infinite process and those desiring to do so should be lauded.

We as humans almost try to know everything, yet we do not truly know ourselves. This is a cognitive bias of ours. For example, when we try to understand the exteral world, we lack the ability to have a complete overview of it. This can be confusing to individuals because some people think the truth lies outside the mind, therefore, they seek it through the external world. We tend to adopt a certain set of beliefs, sort of like a guiding framework at which point it truly becomes our own and it boosts us for the next level. The ultimate truth is that we cannot get our truths from observations of the exteral world. The unexplained forces and other natural phenomenon that we plague with our curiosity and criticism is an example of what humans so merely know.

Unfortunately, we must as humans attempt to contemlpate these questions based on information we have collected ourselves. We come to find out many times that we could not link ideas or collect corroborating information that agreed with a particular understanding or beleif of how something is operating. This is no doubt because we are often right, but for the wrong reasons in regaurds to many of the facts that we begin with, trying to make incoming facts fit into a puzzle in witch it does not belong.

According to all religions scriptures God Almighty is all Light(Spiritually -soul Light) and He had his Light kingdom ( Supreme Sphere ). No one knew except Father, son and Holy Ghost.
They were trice but one God Supreme Light and lives in that sphere which bible describes it is Eternal Kingdom of God Almighty, but God Almighty also created physical world in the begging of creation god formed Gases of diffrent chemicals and all were united and later some time gases were become matter at last a big Globe formed.

Then God said Let “There be Light”. (Starting of big Bang). so we knew what happened i.e.,expansion of Universe.

This is not really a “new” theory at all. The ancient sages of Hinduism advanced the theory of the cosmos being born, running its course, dying, and then being reborn again…for eternity. In the words of Eknath Easwaran: “Just as the day follows night in eternal, unvarying rhythm, so does the entire universe undergo cycles of creation, death, and new birth. As the Day of Brahma dawns, the cosmos comes into being; as the Day comes to an end, the entire creation dies and ceases to exist. Then, for a night as long as the Cosmic Day-the universe rests. Then, without deviating from the eternal rhythm, the cosmos is reborn when Night is over.”

A decade or two ago scientists were surprised to discover that the expansion of the universe was actually accelerating, i.e. in relation to the question: will the expansion reverse itself eventually–will the universe collapse upon itself at some point? Well, from the Hindu perspective, it may do just that, but not for perhaps another 120 billion years (as in, many many years after our sun has depleted its hydrogen and helium and humankind is history). In essence, these startling mysteries that conflict with the laws of physics are all made possible through the consciousness of Brahman (God), the unchanging power that governs all that changes.

My science background is limited ( blame it on an inept 9th grade algebra II teacher….or my lack of aptitude), but I find the issue of the BB, time and when it started and what it is,and what existed before the BB absolutely mesmerizing. Keep thinking!!!!

These ideas are nothing new under the sun. The Stoics and Hindus both proposed an infinite succession of generations and reabsorptions of the universe, as did the Greek philosopher Empedocles, though, for him, this was due to the cosmic forces of love and srife. When love predominates, everything is brought together into a stable unity; when strife prevails, everything is dissevered into chaotic multiplicity. In the language of stoicism, paringenesis means expansion; ekpyrosis, the great conflagration, when all things are reabsorbed once more into God at the end of a great year. The Greek philosophers often speak of the universe as an animal, which scientists like Einstein and Hawking imitate. Einstein described the universe as a mollusc to evoke the spiralling contours and melded fibres of space/time. Reading them one can almost imagine the entire process of this expansion and contraction as the universe drawing breath and exhaling. The Hindus, moreover, actually predict the time our universe will be destroyed pretty accurately in the light of modern science, especially considering their lack of the scientific tools we have today.

These ideas are nothing new under the sun. The Stoics and Hindus both proposed an infinite succession of generations and reabsorptions of the universe, as did the Greek philosopher Empedocles, though, for him, this was due to the cosmic forces of love and srife. When love predominates, everything is brought together into a stable unity; when strife prevails, everything is dissevered into chaotic multiplicity. In the language of stoicism, palingenesis stands for generation and expansion; ekpyrosis, the great conflagration, when all things are reabsorbed once more into God at the end of a great year. I should also say Christ also mentions palingenesis: when the new heaven and earth will be created.

The Greek philosophers often speak of the universe as an animal, which scientists like Einstein and Hawking imitate. Einstein described the universe as a mollusc to evoke the spiralling contours and melded fibres of space/time. Reading them one can almost imagine the entire process of this expansion and contraction as the universe drawing breath and exhaling. The Hindus, moreover, actually predict the time our universe will be destroyed pretty accurately in the light of modern science, especially considering their lack of modern scientific tools.

I always liked the idea that God is eternal and created not just this universe’s big bang but many others. But just because I like this idea doesn’t mean it holds any water. Of course I like it, it’s easy and doesn’t cause me to think that critically. I’m not negating the theory of a higher intelligence but if I had to think beyond my spiritual upbringing I would suggest that there are 2 possibilities in my mind concerning this topic. One would be that our current universe is eternal and has always existed maybe even being destroyed then created again in the past. Two: There are multiple universe’s that exist side by side or even overlapping each other sometimes. I know there will be a time when we know more. We’re an evolving species. It saddens me that when that time comes, I probably won’t be alive to see the knowledge unfold. To me, this is one of the greatest questions of mankind.

Mr bojowald without defining a beginning time means nothing so saying there was a Big Bang before the Big Bang as a theory does little to advance thinking on the topic without at least trying to anchor it to a definition of beginning.

How about :
Our bit of the universe is oscillating between partially expanded and partially contracted.
No BB, no big freeze.
From our perspective, it’s always existed like that.
Consider a sine cycle where 90 and 270 degrees are expanded and contracted respectively.
We’re at about 280 degrees, where contraction has started to reduce, = to accellerating expansion relative to the contracted state at 270 degrees.
Other bits of the universe have their own oscillations.
Our observable bit, viewed at the largest scale, indicates a foam structure.
Our miniscule corner is somewhere in the foam’s structure.

The total universe may just be a foam cushion with someones bum just leaving, allowing the foam to expand…